Windows 10 Menu Disappeared

Yesterday when I clicked on the Start Windows 10 Icon, nothing happened. I was going to turn the computer off. I right clicked it and a black menu popped up with white lettering. This happened several days ago. I was going to write and ask about it, but it mysteriously restored itself. Turning the computer on and off and back on doesn't help. Running Troubleshooting doesn't fix it. I'm not sure what combination of keys I am hitting to cause it to disappear or how I got it back. If anyone else has had this problem, let me know how you corrected it. Thanks. I can work without it, but sometimes its needed.